enum-traits: traits for enums

at the moment, the only trait is DiscriminantValues, defined as:

pub unsafe trait DiscriminantValues {
	type Discriminant: 'static + Clone + Copy + std::fmt::Debug + Eq
		+ PartialEq<Self::Discriminant> + std::hash::Hash + Send + Sync + Unpin;
	
	const VALUES: &'static [Self::Discriminant];
}

which can be derived with #[derive(enum_traits::DiscriminantValues)] on any enum with a #[repr(Int)], where Int is a type in std::primitive.